Congenital hypoplasia of the lumbar pedicle with spondylolisthesis: report of 2 cases

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Congenital hypoplasia of the spinal pedicle is a rare condition. Previously reported cases were treated conservatively or with posterior instrumented fusion. However, the absence or hypoplasia of the lumbar pedicle may increase the difficulty of pedicle screw fixation and fusion. Herein, the authors describe 2 cases of rare adult congenital hypoplasia of the right lumbar pedicles associated with spondylolisthesis. The patients underwent anterior lumbar interbody fusion with a stand-alone cage as well as percutaneous pedicle screw fixation. This method was used to avoid the difficulties associated with pedicle screw fixation and to attain solid fusion. Both patients achieved satisfactory outcomes after a minimum of 2 years of follow-up. This method may be an alternative for patients with congenital hypoplasia of the lumbar spinal pedicle.

ABBREVIATIONSALIF = anterior lumbar interbody fusion; MRC = Medical Research Council; PPF = percutaneous pedicle screw fixation; VAS = visual analog scale.

Congenital hypoplasia of the spinal pedicle is a rare condition. Previously reported cases were treated conservatively or with posterior instrumented fusion. However, the absence or hypoplasia of the lumbar pedicle may increase the difficulty of pedicle screw fixation and fusion. Herein, the authors describe 2 cases of rare adult congenital hypoplasia of the right lumbar pedicles associated with spondylolisthesis. The patients underwent anterior lumbar interbody fusion with a stand-alone cage as well as percutaneous pedicle screw fixation. This method was used to avoid the difficulties associated with pedicle screw fixation and to attain solid fusion. Both patients achieved satisfactory outcomes after a minimum of 2 years of follow-up. This method may be an alternative for patients with congenital hypoplasia of the lumbar spinal pedicle.

ABBREVIATIONSALIF = anterior lumbar interbody fusion; MRC = Medical Research Council; PPF = percutaneous pedicle screw fixation; VAS = visual analog scale.

Congenital hypoplasia of the spinal pedicle is an uncommon anomaly. When it occurs, it mostly involves the cervical or thoracic spine; the absence of a lumbar or sacral pedicle is rare.3,5,6,9,20,21,26 The majority of cases with an absence or hypoplasia of the lumbosacral pedicles are asymptomatic, and they are usually discovered incidentally. Low-back pain is the most frequently reported symptom.6 The rarer cases present with intractable low-back pain or neurological impairment requiring surgery. Most patients are treated with posterior instrumented fusion; however, hypoplasia of the lumbar pedicle may increase the difficulties associated with the pedicle screw fixation and fusion. Herein, we present 2 cases of unilateral hypoplasia of the pedicles in the lumbar spine with concurrent spondylolisthesis, leading to low-back pain and radicular pain of the lower extremities. The surgical strategy in these cases consisted of anterior lumbar interbody fusion (ALIF), followed by percutaneous pedicle screw fixation (PPF) without posterior decompression.

Case Reports

Case 1

History and Examination

A 63-year-old man presented with chronic low-back pain and severe radicular pain in the right lower extremity. Prior conservative treatment with physical therapy and medication was unsuccessful. Physical examination revealed decreased muscle power in bilateral big toe dorsiflexion (Grade 4/5 on the Medical Research Council [MRC] motor scale).19 All modalities of sensation were intact. To assess low-back and radicular pain, we used a visual analog scale (VAS) for pain (0 indicated no pain; 10 indicated the worst pain). Preoperative VAS scores for low-back and leg pain were 6 and 8, respectively. The deep tendon reflexes were 2+ bilaterally. The standing weight-bearing radiographs of the lumbar spine revealed hypoplasia of the right L-4 pedicle and Meyerding Grade I spondylolisthesis at the L4–5 level (Fig. 1).13 A CT scan of the lumbar spine revealed hypoplasia of the right L-4 pedicles and articulating processes (Fig. 2 left). On the left side, there was degeneration of the L4–5 facet joints, with fracture of the pars interarticularis (Fig. 2 right).

FIG. 1.
FIG. 1.

Case 1. Left: Anteroposterior radiograph of the lumbosacral spine reveals hypoplasia of the right L-4 lumbar pedicle (arrowhead). Right: Lateral view. A neutral weight-bearing radiograph shows Meyerding Grade I spondylolisthesis at the L4–5 level.

FIG. 2.
FIG. 2.

Case 1. Axial and sagittal CT (without contrast) scans of the lumbosacral junction. Left: An axial reconstruction of spinal CT scans demonstrates congenitally hypoplastic right L-4 pedicles and articulating processes (arrowhead). Right: The severely degenerated hyperplastic contralateral L4–5 facet joints including the fracture of the pars interarticularis (arrowhead).

Treatment

We performed an ALIF with the SynFix system (Synthes Spine Inc.) and screws. The percutaneous pedicle screws were fixed via the paramedian approach on the left side of L4–5. Posterior decompression was not performed during surgery.

Postoperative Course

The patient's postoperative VAS scores for low-back and radicular pain reduced to 1 and 0, respectively. Physical examination revealed normalization of muscle power in bilateral big toe dorsiflexion (MRC Grade 5/5). The dynamic radiograph of the lumbosacral spine revealed bony fusion with no evidence of pseudarthrosis at the 2-year follow-up (Fig. 3).

FIG. 3.
FIG. 3.

Case 1. Six-month postoperative radiographs. Left: Anteroposterior view. Right: Lateral view. The patient was treated with ALIF using a SynFix cage and left-sided pedicle screw fixation.

Case 2

History and Examination

An 84-year-old man presented with chronic low-back pain and radicular pain that radiated to the bilateral lower extremities. Preoperative VAS scores for the low-back and radicular pain were both 8. Physical examination revealed decreased muscle power in both right and left big toe dorsiflexion (MRC Grades 2/5 and 4/5, respectively). There was also a reduction in the power of bilateral ankle dorsiflexion (MRC Grade 4/5 bilaterally). All modalities of sensation were intact. The deep tendon reflexes were 2+ bilaterally. The standing weight-bearing radiographs of the lumbar spine revealed hypoplasia of the right L-5 pedicle and Meyerding Grade I spondylolisthesis at the L4–S1 level (Fig. 4). A CT scan of the lumbar spine demonstrated hypoplasia of the right L-5 pedicle, fracture of the L-5 pedicle root, and L4–5 foraminal stenosis (Fig. 5).

FIG. 4.
FIG. 4.

Case 2. Left: Anteroposterior radiograph of the lumbosacral spine reveals spondylosis and mild scoliosis. Right: A neutral weight-bearing radiograph shows spondylosis and Meyerding Grade I spondylolisthesis at the L4–S1 level.

FIG. 5.
FIG. 5.

Case 2. Sagittal and axial CT scans (without contrast) of the lumbosacral junction. Left: This sagittal reconstruction of spinal CT scans demonstrates hypoplasia of the right L-5 pedicle (arrowhead) and L4–5 foraminal stenosis. Right: An axial reconstruction of spinal CT scans demonstrates hypoplasia of the right L-5 pedicle (arrow) and pedicle defect.

Treatment

The patient's low-back and radicular pain did not improve with conservative treatment; therefore, we performed an ALIF using the SynFix system with screws at the L4–5 and L5–S1 levels. Additionally, we used PPF via the paramedian approach bilaterally at the L-4 and S-1 levels. Posterior decompression was not performed during surgery. The pedicle screws were augmented with polymethylmethacrylate (PMMA) cement due to severe osteoporosis (bone mineral density of the femoral neck −3.3).

Postoperative Course

The patient's postoperative VAS scores for low-back and radicular pain reduced to 1 and 0, respectively. Physical examination revealed improved muscle power in bilateral big toe dorsiflexion: MRC Grades 4/5 and 5/5 on the right and left sides, respectively. Additionally, bilateral ankle dorsiflexion normalized to MRC Grade 5/5. The dynamic radiograph of the lumbosacral spine revealed solid bony fusion with no evidence of pseudarthrosis at the 2-year follow-up (Fig. 6).

FIG. 6.
FIG. 6.

Case 2. Six-month postoperative radiographs. Left: Anteroposterior view. Right: Lateral view. The patient underwent ALIF with SynFix cages and screws over L4–5 and L5–S1, and bilateral L-4 and S-1 pedicle screw fixation.

Discussion

Dysgenesis or agenesis of the spinal pedicle is thought to result from a large retrosomatic cleft during embryological development.20 These clefts can occur in a variety of locations within the vertebral arch. They can also occur in the pedicles and have been reported from levels T-12 to S-1.4,5 Their cause is uncertain.24 Congenital hypoplasia of a pedicle at the lumbosacral junction can result in accompanying dysfunction or deformity of the facet joint, which is more critical to biomechanical stability than the hypoplasia of the pedicle itself.6

The main role of facet joints in the lumbosacral spine is to stabilize extension and rotation stress.11,22 Biomechanical tests have revealed that total unilateral facetectomy significantly increases the instability of the lumbosacral spine axial rotation and flexion.1 Another function of the facet joint is to distribute the axial load at each level. The load carried by facet joints varies from 9% (neutral) to 15% (extension). If one of these joints is incompetent, the contralateral joint must bear a greater load.8 Case 1 in this study showed a similar type of overload and instability in the lumbar spine, resulting in severe degenerative changes in the contralateral L4–5 facet joints. Kaito et al.6 reported a similar case that was missing the right L-5 pedicle, which led to severe degenerative changes in the contralateral facet joint.

Radiological evaluation of these patients typically begins with conventional radiography and frequently includes CT, myelography, and MRI.17,23 According to Wiener et al.,25 this congenital anomaly has the following radiographic features: 1) the false appearance of an enlarged ipsilateral neural foramen because of the absent pedicle; 2) a dysplastic, dorsally displaced ipsilateral articular pillar and lamina; and 3) a dysplastic ipsilateral transverse process. The spectrum of this anomaly also includes the absence of the ipsilateral pillar or the entire ipsilateral neural arch, as well as other osseous anomalies in more than half of the cases.

The main data collected from the literature are shown in Table 1. Previously reported cases of pedicle hypoplasia or absence were mostly asymptomatic; if present, the only symptom was low-back pain that was well controlled by conservative treatment.12,14,15,21,27 The rarer cases presenting with intractable low-back pain or neurological impairment required surgery.6,17,18 Most of the patients were treated with posterior instrumented fusion. However, lumbar pedicle hypoplasia can increase the difficulties associated with pedicle screw fixation and fusion.

TABLE 1.

Literature summary of cases of hypoplasia or absence of lumbar pedicle

Authors & YearLevel & No. of CasesAge (yrs)/SexSigns & SymptomsRadiological FindingsManagementOutcomeFU
Patel et al., 2013Bilat L-5, 113/FLBP, radiculopathyBilat hypoplasia of L-5 VB & pedicle; spondylolisthesis Grade IPI over L-4 & S-1, w/o decompressionResolution of pain & good bony fusion18 mos
Lt S-1, 110/FLBP, radiculopathyAbsent lt S-1 pedicle, Grade I anterolisthesisPI over bilat L-5, rt S-1 & lt S-1 alar screw w/o decompressionResolution of pain & good bony fusion5 mos
Kaito et al., 2005Rt L-5, 154/MLBP, radiculopathyAbsence of rt L-5 pedicleConservative treatmentNRNR
Sener et al., 1991Rt L-5, 134/MLBPAbsence of rt L-5 pedicleConservative treatmentNRNR
Polly & Mason, 1991Rt L-6, 112/FLBP, radiculopathyAbsence of rt L-6 pedicle, conjoined nerve root at L6–S1NRNRNR
Rt L-4, 114/MLBPAbsence of rt L-4, T-L scoliosisConservative treatmentResolution of pain6 mos
Lt L-5, 119/FLBPAbsence of rt L-5 pedicleL4–S1 PLFResolution of painNR
Rt L-5, 117/MLBPAbsence of rt L-5 pedicle, spondylolysisPLFResolution of painNR
Mizutani et al., 1989Lt L-1, 110/MLBPAbsence of lt L-1 pedicle & VB, hypoplasia of lt T-12, L-2, L-3, & L-5 pediclesConservative treatmentResolution of pain2 yrs
Lederman & Kaufman, 1986T11–12, 112/MNonspecific ab pain, no LBPHypoplasia of lt T-11 pedicle, absence of rt T-12 pedicleNo further workup or therapyNo back painNR
ab = abdominal; FU = follow-up; LBP = low-back pain; NR = not reported; PI = posterior instrumentation; PLF = posterior lateral fusion; T-L = thoracolumbar; VB = vertebral body.

The optimal surgical method for spondylolisthesis remains controversial. Several authors have demonstrated the effectiveness of ALIF in terms of the following advantages: preservation of posterior midline complexes, low risk of neural complication, less blood loss, and high fusion rate. Although a stand-alone ALIF cage is an effective construct for low-grade spondylolisthesis, nonunion and pseudarthrosis are possible complications. Recent studies have shown that ALIF with PPF can be performed to attain the surgical goals and successful outcomes in the management of isthmic spondylolisthesis.2,7 However, hypoplasia of the lumbar pedicle also increases the difficulty of performing PPF. In the cases featured in this paper, we performed PPF only for normal pedicles. We used a stand-alone cage augmented with screws to increase stability given concerns of pseudarthrosis. Both patients underwent the combined procedures without posterior decompression, and solid fusions were achieved.

Although Patel et al. also performed posterior instrumented fusion without decompression,17 2-level fusion was applied in their patients. In our study, both patients underwent only single-level fusion; this allowed for the preservation of adjacent normal spinal segments. Our patients reported satisfactory functional outcomes at the 2-year follow-up. Anterior lumbar interbody fusion with a stand-alone cage followed by PPF avoids the difficulties associated with pedicle screw fixation and provides sufficient fusion stability. Percutaneous pedicle screw fixation has the advantages of a shorter surgical time, less paraspinal muscle damage, and lower blood loss, compared with open pedicle screw fixation. The procedures performed in our cases resulted in favorable clinical outcomes and fusion. Further studies are necessary to corroborate our results.

Conclusions

Congenital hypoplasia of the lumbar spine pedicle is rare. Therefore, it is important to recognize this anomaly as an unusual cause of low-back and radicular pain. Lumbar pedicle hypoplasia can increase the difficulty of pedicle screw fixation and fusion. Anterior lumbar interbody fusion with a stand-alone cage followed by PPF can provide solid fusions and avoid the difficulties associated with pedicle screw fixation, as demonstrated in our 2 adult patients, in whom successful fusion and satisfactory functional outcomes were reported at the 2-year followup. This method may be an alternative for patients with congenital hypoplasia of the lumbar spinal pedicle with spondylolisthesis.

Acknowledgments

This study was supported by a grant from the Wooridul Spine Hospital.

References

  • 1

    Abumi KPanjabi MMKramer KMDuranceau JOxland TCrisco JJ: Biomechanical evaluation of lumbar spinal stability after graded facetectomies. Spine (Phila Pa 1976) 15:114211471990

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 2

    Choi KCKim JSShim HKAhn YLee SH: Changes in the adjacent segment 10 years after anterior lumbar interbody fusion for low-grade isthmic spondylolisthesis. Clin Orthop Relat Res 472:184518542014

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 3

    De Boeck MDe Smedt EPotvliege R: Computed tomography in the evaluation of a congenital absent lumbar pedicle. Skeletal Radiol 8:1971991982

  • 4

    Dietemann JLMacedo RMedjek LBabin EWackenheim A: [Bilateral pedicular cleft in a patient with neurofibromatosis (author's transl).]. Ann Radiol (Paris) 24:6656671981. (Fr)

    • Search Google Scholar
    • Export Citation
  • 5

    Johansen JGMcCarty DJHaughton VM: Retrosomatic clefts: computed tomographic appearance. Radiology 148:4474481983

  • 6

    Kaito TKato YSakaura HYamamoto KHosono N: Congenital absence of a lumbar pedicle presenting with contralateral lumbar radiculopathy. J Spinal Disord Tech 18:2032052005

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 7

    Kim KHLee SHLee DYShim CSMaeng DH: Anterior bone cement augmentation in anterior lumbar interbody fusion and percutaneous pedicle screw fixation in patients with osteoporosis. J Neurosurg Spine 12:5255322010

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 8

    Kornberg M: Spondylolisthesis with unilateral pars interarticularis defect and contralateral facet joint degeneration. A case report. Spine (Phila Pa 1976) 13:7127131988

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 9

    Lauten GJWehunt WD: Computed tomography in absent cervical pedicle. AJNR Am J Neuroradiol 1:2012031980

  • 10

    Lederman HMKaufman RA: Congenital absence and hypoplasia of pedicles in the thoracic spine. Skeletal Radiol 15:2192231986

  • 11

    Lorenz MPatwardhan AVanderby R Jr: Load-bearing characteristics of lumbar facets in normal and surgically altered spinal segments. Spine (Phila Pa 1976) 8:1221301983

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 12

    Macleod SHendry GM: Congenital absence of a lumbar pedicle. A case report and a review of the literature. Pediatr Radiol 12:2072101982

  • 13

    Meyerding HW: Spondylolisthesis. Surg Gynecol Obstet 54:3713791932

  • 14

    Mizutani MYamamuro TShikata J: Congenital absence of a lumbar pedicle. Spine (Phila Pa 1976) 14:8908911989

  • 15

    Morin MEPalacios E: The aplastic hypoplastic lumbar pedicle. Am J Roentgenol Radium Ther Nucl Med 122:6396421974

  • 16

    Oh YMEun JP: Congenital absence of a cervical spine pedicle: report of two cases and review of the literature. J Korean Neurosurg Soc 44:3893912008

  • 17

    Patel AJVadivelu SDesai SKJea A: Congenital hypoplasia or aplasia of the lumbosacral pedicle as an unusual cause of spondylolisthesis in the pediatric age group. J Neurosurg Pediatr 11:7177212013

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 18

    Polly DW JrMason DE: Congenital absence of a lumbar pedicle presenting as back pain in children. J Pediatr Orthop 11:2142191991

  • 19

    Seddon HJ: Peripheral Nerve Injuries. LondonHM Stationery Office1954

  • 20

    Sener RN: Sacral pedicle agenesis. Comput Med Imaging Graph 21:3613631997

  • 21

    Sener RNRipeckyj GTJinkins JR: Agenesis of a lumbar pedicle: MR demonstration. Neuroradiology 33:4641991

  • 22

    Sharma MLangrana NARodriguez J: Role of ligaments and facets in lumbar spinal stability. Spine (Phila Pa 1976) 20:8879001995

  • 23

    Sheehan JKaptain GSheehan JJane J Sr: Congenital absence of a cervical pedicle: report of two cases and review of the literature. Neurosurgery 47:143914422000

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 24

    Soleimanpour MGregg MLParaliticci R: Bilateral retrosomatic clefts at multiple lumbar levels. AJNR Am J Neuroradiol 16:161616171995

  • 25

    Wiener MDMartinez SForsberg DA: Congenital absence of a cervical spine pedicle: clinical and radiologic findings. AJR Am J Roentgenol 155:103710411990

  • 26

    Wortzman GSteinhardt MI: Congenitally absent lumbar pedicle: a reappraisal. Radiology 152:7137181984

  • 27

    Yousefzadeh DKEl-Khoury GYLupetin AR: Congenital aplastic-hypoplastic lumbar pedicle in infants and young children. Skeletal Radiol 7:2592651982

Disclosures

The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

Author Contributions

Drafting the article: Hsieh. Critically revising the article: SH Lee. Administrative/technical/material support: HC Lee, Hsieh, Chen. Study supervision: HC Lee, SH Lee, Oh, Hwang, Park.

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Article Information

Contributor Notes

INCLUDE WHEN CITING Published online January 6, 2017; DOI: 10.3171/2016.8.SPINE151137.Correspondence Hyung Chang Lee, Department of Cardiovascular Surgery, Wooridul Spine Hospital, Gimpo Airport, 70 Haneulgil, Gangseo-gu, Seoul 155-823, Korea. email: drhclee@yahoo.com.

© AANS, except where prohibited by US copyright law.

Headings
Figures
  • View in gallery

    Case 1. Left: Anteroposterior radiograph of the lumbosacral spine reveals hypoplasia of the right L-4 lumbar pedicle (arrowhead). Right: Lateral view. A neutral weight-bearing radiograph shows Meyerding Grade I spondylolisthesis at the L4–5 level.

  • View in gallery

    Case 1. Axial and sagittal CT (without contrast) scans of the lumbosacral junction. Left: An axial reconstruction of spinal CT scans demonstrates congenitally hypoplastic right L-4 pedicles and articulating processes (arrowhead). Right: The severely degenerated hyperplastic contralateral L4–5 facet joints including the fracture of the pars interarticularis (arrowhead).

  • View in gallery

    Case 1. Six-month postoperative radiographs. Left: Anteroposterior view. Right: Lateral view. The patient was treated with ALIF using a SynFix cage and left-sided pedicle screw fixation.

  • View in gallery

    Case 2. Left: Anteroposterior radiograph of the lumbosacral spine reveals spondylosis and mild scoliosis. Right: A neutral weight-bearing radiograph shows spondylosis and Meyerding Grade I spondylolisthesis at the L4–S1 level.

  • View in gallery

    Case 2. Sagittal and axial CT scans (without contrast) of the lumbosacral junction. Left: This sagittal reconstruction of spinal CT scans demonstrates hypoplasia of the right L-5 pedicle (arrowhead) and L4–5 foraminal stenosis. Right: An axial reconstruction of spinal CT scans demonstrates hypoplasia of the right L-5 pedicle (arrow) and pedicle defect.

  • View in gallery

    Case 2. Six-month postoperative radiographs. Left: Anteroposterior view. Right: Lateral view. The patient underwent ALIF with SynFix cages and screws over L4–5 and L5–S1, and bilateral L-4 and S-1 pedicle screw fixation.

References
  • 1

    Abumi KPanjabi MMKramer KMDuranceau JOxland TCrisco JJ: Biomechanical evaluation of lumbar spinal stability after graded facetectomies. Spine (Phila Pa 1976) 15:114211471990

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 2

    Choi KCKim JSShim HKAhn YLee SH: Changes in the adjacent segment 10 years after anterior lumbar interbody fusion for low-grade isthmic spondylolisthesis. Clin Orthop Relat Res 472:184518542014

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 3

    De Boeck MDe Smedt EPotvliege R: Computed tomography in the evaluation of a congenital absent lumbar pedicle. Skeletal Radiol 8:1971991982

  • 4

    Dietemann JLMacedo RMedjek LBabin EWackenheim A: [Bilateral pedicular cleft in a patient with neurofibromatosis (author's transl).]. Ann Radiol (Paris) 24:6656671981. (Fr)

    • Search Google Scholar
    • Export Citation
  • 5

    Johansen JGMcCarty DJHaughton VM: Retrosomatic clefts: computed tomographic appearance. Radiology 148:4474481983

  • 6

    Kaito TKato YSakaura HYamamoto KHosono N: Congenital absence of a lumbar pedicle presenting with contralateral lumbar radiculopathy. J Spinal Disord Tech 18:2032052005

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 7

    Kim KHLee SHLee DYShim CSMaeng DH: Anterior bone cement augmentation in anterior lumbar interbody fusion and percutaneous pedicle screw fixation in patients with osteoporosis. J Neurosurg Spine 12:5255322010

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 8

    Kornberg M: Spondylolisthesis with unilateral pars interarticularis defect and contralateral facet joint degeneration. A case report. Spine (Phila Pa 1976) 13:7127131988

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 9

    Lauten GJWehunt WD: Computed tomography in absent cervical pedicle. AJNR Am J Neuroradiol 1:2012031980

  • 10

    Lederman HMKaufman RA: Congenital absence and hypoplasia of pedicles in the thoracic spine. Skeletal Radiol 15:2192231986

  • 11

    Lorenz MPatwardhan AVanderby R Jr: Load-bearing characteristics of lumbar facets in normal and surgically altered spinal segments. Spine (Phila Pa 1976) 8:1221301983

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 12

    Macleod SHendry GM: Congenital absence of a lumbar pedicle. A case report and a review of the literature. Pediatr Radiol 12:2072101982

  • 13

    Meyerding HW: Spondylolisthesis. Surg Gynecol Obstet 54:3713791932

  • 14

    Mizutani MYamamuro TShikata J: Congenital absence of a lumbar pedicle. Spine (Phila Pa 1976) 14:8908911989

  • 15

    Morin MEPalacios E: The aplastic hypoplastic lumbar pedicle. Am J Roentgenol Radium Ther Nucl Med 122:6396421974

  • 16

    Oh YMEun JP: Congenital absence of a cervical spine pedicle: report of two cases and review of the literature. J Korean Neurosurg Soc 44:3893912008

  • 17

    Patel AJVadivelu SDesai SKJea A: Congenital hypoplasia or aplasia of the lumbosacral pedicle as an unusual cause of spondylolisthesis in the pediatric age group. J Neurosurg Pediatr 11:7177212013

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 18

    Polly DW JrMason DE: Congenital absence of a lumbar pedicle presenting as back pain in children. J Pediatr Orthop 11:2142191991

  • 19

    Seddon HJ: Peripheral Nerve Injuries. LondonHM Stationery Office1954

  • 20

    Sener RN: Sacral pedicle agenesis. Comput Med Imaging Graph 21:3613631997

  • 21

    Sener RNRipeckyj GTJinkins JR: Agenesis of a lumbar pedicle: MR demonstration. Neuroradiology 33:4641991

  • 22

    Sharma MLangrana NARodriguez J: Role of ligaments and facets in lumbar spinal stability. Spine (Phila Pa 1976) 20:8879001995

  • 23

    Sheehan JKaptain GSheehan JJane J Sr: Congenital absence of a cervical pedicle: report of two cases and review of the literature. Neurosurgery 47:143914422000

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 24

    Soleimanpour MGregg MLParaliticci R: Bilateral retrosomatic clefts at multiple lumbar levels. AJNR Am J Neuroradiol 16:161616171995

  • 25

    Wiener MDMartinez SForsberg DA: Congenital absence of a cervical spine pedicle: clinical and radiologic findings. AJR Am J Roentgenol 155:103710411990

  • 26

    Wortzman GSteinhardt MI: Congenitally absent lumbar pedicle: a reappraisal. Radiology 152:7137181984

  • 27

    Yousefzadeh DKEl-Khoury GYLupetin AR: Congenital aplastic-hypoplastic lumbar pedicle in infants and young children. Skeletal Radiol 7:2592651982

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